The present invention relates to a method for manufacturing a display panel constructed from a pair of connected substrates, and in particular to a method for applying a bonding agent to the substrates.
An AC-type plasma display panel (hereafter abbreviated to PDP) is a type of gas discharge panel, well-known in the art as one example of a display panel.
A PDP is illustrated in FIG. 42. Here, the PDP is constructed from a front substrate 2000 and a back substrate 2100. The front substrate 2000 is generally produced by forming discharge electrodes 2002 upon a front glass plate 2101. This structure is then covered with a dielectric glass layer 2003 and a protective layer of magnesium oxide (MgO) 2004.
The back substrate 2100 is formed by arranging address electrodes 2102, barrier ribs 2103 and a phosphor layer 2104 on a back glass plate 2101. The front substrate 2000 and the back substrate 2001 are then fixed together, and discharge spaces 2200 are formed by introducing a discharge gas into the spaces demarcated by the barrier ribs 2103. Cells are formed in the discharge spaces 2200 at the points where discharge electrodes 2002 and address electrodes 2102 intersect. FIG. 42 shows only one such cell, but in fact the PDP normally includes a plurality of cells in which the phosphor layer 2104 is composed of alternating red, green and blue phosphors, enabling a color display to be produced. Note that in the drawing, the discharge electrodes 2002 and the address electrodes 2102 are drawn as if arranged in parallel, but in fact they are arranged at right angles.
A discharge gas, such as a mixture of neon and xenon, is normally enclosed into the discharge spaces 2200 at a pressure of around 500 Torr (6.65xc3x97104 Pa).
In practice, however, such conventional PDPs have not always been able to achieve satisfactory luminance. In order to improve luminance, it is considered necessary to enclose the discharge gas inside the discharge spaces 2200 at an internal pressure exceeding 500 Torr (6.65xc3x97104 Pa).
However, with the internal pressure in the discharge spaces 2200 is raised to 760 Torr (1.01xc3x97105 Pa) or 1000 Torr (1.33xc3x97105 Pa), for example, gaps are generated between the barrier ribs 2103 formed on the back glass plate 2101 and the front substrate 2000, while the front and back substrates 2000 and 2100 bulge outwards. This means that neighboring discharge spaces 2200 are no longer effectively divided by the barrier ribs 2103, causing the display performance of the PDP to deteriorate.
Even if the internal pressure is set at 760 Torr (1.01xc3x97105 Pa) or less, the barrier ribs 2103 are not connected to the front substrate 2100, so that external vibrations or vibrations caused by driving the PDP itself bring the barrier ribs 2103 and the front substrate 2000 repeatedly into contact, generating noise.
In order to correct these problems, one related technique has proposed that the topmost edge of the barrier ribs 2103 be coated with a bonding agent before fixing the pair of substrates together to form the discharge spaces 2200. A gas discharge panel in which gas has been sealed at a higher pressure is produced, realizing an improvement in luminance. Such a procedure is described in Japanese Patent Application No. 9-49006.
However, when a well-known method such as screen-printing is used to apply the bonding agent to the topmost edge of the barrier ribs 2103, it is difficult to apply the bonding agent equally to the very long and narrow top surfaces of the barrier ribs 2103 without leaving some parts uncovered. In the case of screen-printing, matching an aperture pattern accurately to the shape of the barrier ribs 2103 has proved extremely difficult. As a result, finding a simple method for improving bonding strength, while maintaining display performance and preventing the generation of distortion when the barrier ribs 2103 touch the front substrate 2000 has posed considerable obstacles.
Furthermore, the properties of the dielectric glass layer 2003 covering the electrodes change if exposed to the discharge spaces 2200. As a result, a protective coat of MgO or similar is usually formed to cover the surface of the dielectric glass layer 2003, as described above. Even if a protective layer 2004 is applied in this way, however, the tops of the barrier ribs 2103 are connected after the protective layer 2004 has been applied, and so the surfaces of the bonding agent are not covered by the protective layer 2004. Thus, the properties of the surface of the bonding agent change as a result of exposure to the discharge spaces 2200. Substances produced by this change pollute the discharge spaces 2200 and are the cause of such problems as rises in discharge voltage, falls in discharge efficiency and deterioration in the phosphors.
The present invention has been developed in view of the above problems in the background art. A first object of the invention is to provide a display panel manufacturing method performed by connecting two substrates together as strongly as possible using a bonding agent, and in particular to provide a simple bonding agent application method for arranging the bonding agent evenly on the narrow areas that form the tops o f the barrier ribs leaving almost no uncovered areas.
A second object of the present invention is to provide a gas discharge display panel capable of preventing changes in the properties of the bonding agent surface caused by discharge.
To fulfill the above first object, a display panel manufacturing method, comprising an application process for applying a bonding agent to a plurality of barrier ribs formed on at least one of a pair of substrates, and a connection process for arranging the pair of substrates together via the bonding agent that has been applied to the barrier ribs is provided. The application process includes a bonding agent layer forming step for forming a layer of a past-like bonding agent having an even surface over a substrate having an even surface; and a connecting step for simultaneously bringing a top of each barrier rib down into contact with the bonding agent layer, while regulating a distance between the upper surface of the bonding agent layer and the barrier ribs.
A display panel manufacturing method may further include an application process for applying a bonding agent to a plurality of barrier ribs formed on at least one of a pair of substrates, and a connection process for arranging the pair of substrates in opposition and connecting the pair of substrates together via the bonding agent that has been applied to the barrier ribs. The application process includes a bonding agent layer forming step for forming a layer of a paste-like bonding agent having an even surface so as to embed a position regulating member that regulates positions of the barrier ribs within the layer, the position regulating member being arranged on a substrate having an even surface; and a connecting step for bringing a top of each barrier rib down into contact with the position regulating member to apply the bonding agent simultaneously to the tops of all of the barrier ribs while regulating a distance between the upper surface of the bonding agent layer and the barrier ribs.
Furthermore, a display panel manufacturing method may include an application process for applying a bonding agent to a plurality of barrier ribs formed on at least one of a pair of substrates in opposition and connecting the pair of substrates together via the bonding agent that has been applied to the barrier ribs. The application process includes a bonding agent layer forming step for forming a layer of a paste-like bonding agent having a curved surface so as to embed a position regulating member that regulates positions of the barrier ribs within the layer, the position regulating member being arranged on a substrate having a curved surface; and a connecting step for bringing a part of each barrier rib top down into contact with the position regulating member, and then to move the position regulating member along a length of the barrier ribs to apply the bonding agent to the tops of all of the barrier ribs while regulating a distance between the upper surface of the bonding agent layer and the barrier ribs.
In this way, the invention aligns barrier rib tops and the bonding agent arranged on the barrier rib tops using surface tension created on the surface of the barrier ribs by bringing the barrier rib tops and the surface of a bonding paste layer into the appropriate degree of contact This method is used rather than a screen plate with an aperture pattern like that used in screen-printing. As a result, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, even if the barrier rib tops are not strictly linear, and form wavy lines.
This means that, if a screen-printing method is used when the barrier ribs are arranged in a stripe formation, aligning the barrier ribs w the screen plate is difficult due to slight variations in barrier rib pitch. As a result, when such a conventional technique is used, the barrier rib tops and the bonding agent are not correctly aligned, and the bonding agent cannot be evenly applied to the barrier rib tops. Furthermore, if the barrier ribs are formed in wavy lines, aligning the barrier ribs accurately with the screen plate is more difficult, and applying the bonding agent evenly to the barrier rib tops becomes even more problematic. In contrast, using the present invention enables the bonding agent to be applied evenly to the barrier rib tops without the variations in barrier rib pitch and barrier ribs formed in wavy lines having any impact.
Here, the bonding agent can be applied more liberally to the barrier rib tops for connecting with the front substrate than was possible when it could not be evenly applied, producing a display panel with greater bonding strength.
By attaching the bonding agent to the barrier ribs using surface tension as explained above, the bonding agent can be applied to the barrier rib tops in an ideal shape. This reduces the degree of bond seepage into the cell area, so that the fall in the amount of luminance produced from the front glass plate is limited.
The following is an explanation of the ideal shape in which the bonding agent should be applied to the barrier rib tops. FIG. 41 shows a cross-section of this shape.
As shown in FIG. 41A, the ideal shape for applying the bonding agent 2300 is formed so that the bonding agent 2300 is more thickly applied near the center of the barrier rib top as seen in cross-section, and becomes thinner towards the edges. When the barrier ribs 2103 are connected to the front panel, the bonding agent 2300 oozes out from either side of each barrier rib 2103, as shown by the protruding parts 2301 in the drawing. Such protruding parts 2301 reduce the light-emitting area as seen from the front glass plate by a corresponding amount, causing luminance to deteriorate. Accordingly, the protruding parts 2301 need to be made as small as possible to limit deterioration in luminance. Thus it is preferable for the shape of the bonding agent 2300 before the barrier ribs are connected to be formed so that a thinner coating runs along both sides of the top of each barrier rib 2103.
Here, the relative positions of the barrier ribs and the bonding agent can be altered while keeping the barrier ribs in contact the bonding agent layer. This enables the bonding agent to be applied more evenly to the barrier rib tops.
The bonding agent applying process should preferably be repeated a plurality of times.
The bonding agent may be formed in a layer on the top of a flat plate.
The position regulating member may be made from wire rods, which are either interwoven or lined up precisely. The position regulating member may also be composed of indentations and protrusions formed on the surf are of a flat substrate, or may be a plurality of half-cylinders, the barrier rib tops being brought into contact with the curved surface of the half-cylinders.
If the bonding agent is applied after implementation of a process for leveling the barrier ribs across the entire surface of the substrate so that all the barrier rib tops are at approximately the same height, variations in the amount of bonding agent applied, caused by variations in the height of different barrier ribs or along the length of one barrier rib, are eliminated. This allows the bonding agent to be evenly applied to the barrier rib tops without any irregularities.
In order to achieve the first object, a display panel manufacturing method, for connecting a pair of substrates arranged in opposition via a plurality of barrier ribs formed in a specific pattern on at least one of the substrates and a bonding agent arranged on the barrier ribs is provided. The display panel manufacturing method includes a barrier rib pattern forming process and a bonding agent pattern forming process. These processes include a first step for laminating the bonding agent and a material for forming the barrier ribs by forming layers of certain thicknesses; a second step for simultaneously removing corresponding parts of the laminated barrier rib material and bonding agent to form the specific pattern; and a third step for transferring the pattern formed in the barrier rib forming material and bonding agent to the substrate on which the barrier ribs are to be formed.
Here, the barrier rib tops and the bonding agent arranged on the barrier rib tops are aligned by removing corresponding parts of the barrier rib and bonding agent layers at the same time. The pattern for the barrier ribs and the bonding agent can thus be formed simultaneously. This method is used rather than a screen plate with an aperture pattern like that used in screen-printing. As a result, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, even if the barrier rib tops are not strictly linear, and form wavy lines. This produces a display panel with greater bonding strength.
Also in order to achieve the above first object, a display panel manufacturing method, for connecting a pair of substrates arranged in opposition, via a bonding agent, which has been applied to a plurality of barrier ribs formed in a specific pattern on at least one of the substrates is provided. The display panel manufacturing method includes a barrier rib pattern forming process including a first step for laminating the barrier rib forming material and the bonding agent by forming layers of certain thicknesses; a second step for simultaneously pressing down the laminated barrier rib forming material and bonding agent using a same pattern-forming member to form the specific pattern; and a third step for transferring a molded pattern formed in the barrier rib forming material and bonding agent to the substrate on which the barrier ribs are to be formed.
Here, the barrier rib tops and the bonding agent arranged on the barrier tops are aligned by forming the pattern f or the barrier ribs and the bonding agent simultaneously. This method is used rather than a screen plate with an aperture pattern like that used in screen-printing. As a result, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, even if the barrier rib tops are not strictly linear, and form wavy lines. This produces a display panel with greater bonding strength.
Here, at least one indentation and protrusion is formed on the parts of the pattern-forming member that correspond to top surfaces of the barrier ribs on which the bonding agent is applied.
Here, the alignment of the barrier ribs and the bonding agent is determined by indentations and protrusions, allowing the bonding agent to be arranged more accurately on the barrier rib tops. This produces a display panel with greater bonding strength.
Also, in order to achieve the above first object, a display panel manufacturing method, for connecting a pair of substrates arranged in opposition via a bonding agent arranged on a plurality of barrier ribs formed in a specific pattern on at least one of the substrates is provided. The display panel manufacturing method includes an indentation forming process for forming at least one indentation in a center of each barrier rib top, when viewed widthwise, and a bonding agent arranging process for arranging the bonding agent in the indentations.
The barrier rib tops and the bonding agent arranged on the barrier rib tops are here aligned by indentations formed in advance in the central area of the barrier rib tops. This method is used rather than a screen plate with an aperture pattern like that used in screen-printing. As a result, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, even if the barrier rib tops are not strictly linear, and form wavy lines.
When the bonding agent is arranged on barrier rib tops without indentations, the bonding agent tends to seep off the barrier rib tops. This is another reason why the bonding agent cannot be arranged evenly on the barrier rib tops. Since the bonding agent in the present invention is arranged in the indentations formed in the barrier rib tops, this kind of run-off is prevented, enabling the bonding agent to be applied evenly to the barrier rib tops. As a result, a display panel having greater bonding strength can be obtained.
Additionally, arranging the bonding agent in the indentations prevents the bonding agent from trickling down from the barrier rib tops into the front glass plate side of the panel when firing is performed.
The barrier rib pattern is formed by pressing a pattern-forming member onto the barrier rib forming material, the barrier rib forming material being arranged in a layer of a specific thickness, and the indentation forming process is performed simultaneously with the barrier rib pattern formation when the pattern-forming member is pressed onto the barrier rib forming material.
Here, the bonding agent may be arranged in the indentations using a screen-printing method, or by a method in which the bonding agent is injected into the indentations via a nozzle. Of the several possible methods, the nozzle-injection method is preferred since this method applies the bonding agent to the indentations most accurately.
In order to achieve the first object, a display panel manufacturing method, for connecting a pair of substrates arranged in opposition via a bonding agent arranged on a plurality of barrier ribs formed in a specific pattern on at least one of the substrates is provided. A process for arranging the bonding agent on the barrier ribs includes an attaching process for attaching a bonding agent positioning member to the barrier ribs; a first removing process for removing parts of the bonding agent positioning member attached to the barrier rib tops at positions corresponding to the specific pattern, to form a groove along each barrier rib top; a bonding agent filling process for filling the grooves with the bonding agent, while maintaining the relative positions of the grooves and the barrier rib xe2x80x98tops; and a second removing process for removing the remaining bonding agent positioning member.
Here the barrier rib tops and the bonding agent arranged on the barrier rib tops are aligned based on a pattern formed so that it conforms to the barrier rib pattern. This method is used rather than a screen plate with an aperture pattern like that used in conventional screen-printing techniques. As a result, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, even if the barrier rib tops are not strictly linear, and form wavy lines. This enables a display panel with greater bonding strength to be obtained. Further more, the bonding agent is prevented from flowing off the barrier rib tops by the bonding agent positioning member, until the bonding agent positioning member is removed.
The adhesion process is performed by applying the bonding agent positioning member to the barrier ribs after a connecting layer is formed on either the barrier ribs or the bonding agent positioning member.
The first removing process removes parts of the bonding agent positioning member attached to the barrier rib tops by irradiating the surface of the bonding agent positioning member with a laser.
Here, it is preferable that a material used for the barrier rib tops absorbs laser light more easily than a material used for other parts of the barrier ribs.
The first removing process may form holes in the first member adhering to the barrier rib tops using a grinding method.
Here, if the central area of each barrier rib top is removed in the first removing process, the amount of bonding agent that seeps into the cell area after the panel has been sealed is further reduced.
Here, in the bond agent filling process, the bond agent may be applied using a screen-printing method or a nozzle-injection method.
The second removing process removes the remainder of the first member using peeling, melting and sublimation.
The above first object may also be achieved by a display panel manufacturing method, for connecting a pair of substrates arranged in opposition via a bonding agent applied to a plurality of barrier ribs formed on at least one of the substrates. A process for arranging the bonding agent on the barrier ribs includes an arranging process for bringing an already formed bond sheet into contact with tops of the barrier ribs; a transfer process for transferring the bonding agent to the parts of the barrier rib in contact with the bond sheet by pressing the bond sheet onto the barrier rib tops; and a removing process for separating the bond sheet from the barrier ribs.
Here, the bonding agent in the present invention is arranged on the barrier rib tops with the bonding agent and the barrier rib tops in an accurately aligned state by bringing a bond sheet and the barrier rib tops into contact and transferring the bonding agent selectively to those parts of the barrier rib tops touching the bond sheet. This method is used rather than a screen plate with an aperture pattern like that used in screen-printing. As a result, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, even if the barrier rib tops are not strictly linear, and form wavy lines. This enables a display panel with greater bonding strength to be obtained.
The transfer process should preferably heat the parts of the bond sheet in contact with the barrier rib tops.
This gives the bonding agent greater adhesiveness, enabling it to be transferred to the barrier rib tops with more reliability.
The above first object may also be achieved by a display panel manufacturing method, for connecting a pair of substrates arranged in opposition via a plurality of barrier ribs formed on at least one of the substrates, and a bonding agent applied to the barrier ribs. The display panel manufacturing method includes an applying process for applying the bonding agent to an area on each barrier rib that is at least as large as a top of each barrier rib; a hardening process for selectively hardening parts of the attached bonding agent positioned in a central area of the barrier rib tops, when viewed widthwise; and a removing process for removing the parts of the bonding agent that-have not been hardened.
Here, the application area for the bonding agent is not established from the outset as in screen-printing. Instead, the bonding agent is arranged on the barrier rib tops, covering an area than is wider than the barrier rib tops. Central parts of the arranged bonding agent are then hardened and the parts that still remain soft are selectively removed, leaving the bonding agent arranged appropriately along the barrier rib tops. As a result, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, enabling a display panel with greater bonding strength to be obtained. If the accuracy with which parts of the bonding agent are hardened can be improved, the bonding agent can be applied evenly along the narrow barrier rib tops using a simple technique, even if the barrier rib tops are not strictly linear, and form wavy lines. This enables a display panel with even greater bonding strength to be obtained.
In the applying process, a compound of bonding agent and photo-hardening, resin is applied to the barrier rib tops; and in the hardening process, central parts of the applied compound are exposed to light, causing the exposed parts of the compound to harden.
A resin that hardens upon exposure to ultra-violet light is used as the photo-hardening resin, and the light used in the hardening process may be ultra-violet light.
In the hardening process, after ultra-violet irradiation has taken place, hardened parts of the bonding agent are heated.
This enables the hardened bonding agent to be more firmly hardened.
The bonding agent is arranged on the barrier ribs using a compound including a substance which is more difficult to melt than the bonding agent.
The substance supports the load of the front substrate, preventing bonding agent melted when the substrates are sealed from being pressed down by the weight of the front substrate and seeping into the cell area. This stops the panel from being fired with bonding agent seepage inside the cell area.
Next, to achieve the above second object, the present invention also includes a gas discharge panel, including a first substrate, on which a plurality of pairs of electrodes extending in: a first direction, and a dielectric layer covering the electrodes have been formed, and a second substrate, on which a plurality of barrier ribs, extending in a second direction differing from the first direction, are formed in opposition to the dielectric layer and the electrode pairs so that the barrier ribs are separated from the dielectric layer and the electrode pairs. Here the dielectric layer and the barrier ribs are at least partially connected via a bonding agent. The panel is structured such that discharge mainly occurs in parts of the panel separated from the positions where the barrier ribs and the dielectric layer are connected.
This means that discharge does not occur equally throughout each cell, but is more likely to occur in the parts of a cell distanced from the locations where the barrier ribs are connected than in those parts near to the connected areas. Accordingly, the bonding agent applied to the barrier rib tops is less likely to be exposed to discharge, preventing pigments, residual carbon, and the like from contaminating the discharge gas in the discharge spaces. As a result, increases in discharge voltage, deterioration of the phosphor layer, and reduction in luminance are less likely, and initial operating performance can be sustained over the long term.
The panel structure described above may be formed in a variety of ways, as explained below.
One option is a panel structure in which the gaps between pairs of facing electrodes have both wide and narrow sections, and the narrow sections are formed in the spaces between the parts of the dielectric layer to which the barrier ribs are connected. Another option is a panel structure in which a protective layer covers the surface of the dielectric layer, aside from the parts of the dielectric layer where the barrier ribs are connected. A further option is a panel structure in which the parts of the dielectric layer where the barrier ribs are connected are thicker than the other parts of the dielectric layer. Yet another option is a panel structure in which a protective layer is formed on the surface of the dielectric layer, and the barrier ribs connected to the protective layer, so that the parts of the protective layer where the barrier ribs are connected have less surface roughness than the other parts of the protective layer. Yet another option is a panel structure in which a protective layer is formed on the surface of the dielectric layer, and the barrier ribs connected to the protective layer, so that the parts of the protective layer where the barrier ribs are connected are thicker than the other parts of the protective layer. Yet a further option is a panel structure in which parts of the barrier ribs which do not correspond to cells are attached to the front substrate. Another option is a panel structure in which the barrier ribs are partially connected to the first substrate with a bonding agent, which is applied to the barrier rib tops so that the area covered is narrower than each barrier rib top.
The term xe2x80x98barrier rib topsxe2x80x99 in the last panel structure described above refers to a flat area on the top of each barrier rib, if the barrier ribs have a level upper surface. Alternately, if the tops of the barrier ribs have a curved surface, the term refers to an area determined by a value that is approximately double the size of the radius of the curved surface.
Gas should preferably be enclosed in the space between the 15 first and second substrates of the gas discharge panel at a pressure of not less than 760 Torr (1.01xc3x97105 Pa).